1. Field of the Invention
The present invention relates to an image display apparatus incorporating paired anode substrate and cathode substrate disposed opposite to each other through a spacer and a manufacturing method therefor, and more particularly to an image display apparatus incorporating electron emission units for emitting field electrons and a manufacturing method therefor.
2. Description of the Related Art
In recent years research and development of an image display apparatus have been performed to reduce the thickness of the display unit. Under the present circumstance, a field emission type display apparatus (hereinafter abbreviated as xe2x80x9cFEDxe2x80x9d) incorporating so-called electron emission units has received special attention.
The FED incorporates a cathode substrate having the electron emission unit and an anode substrate having a fluorescent layer and disposed opposite to the cathode substrate. In general, the electron emission units of the cathode substrate are spindt type electron emission units or flat electron emission units. The anode substrate incorporates an anode electrode which is formed below the fluorescent layer and to which anode voltage for accelerating electrons emitted from the electron emission unit is applied.
In the FED, a vacuum state is maintained between the cathode substrate and the anode substrate. Therefore, the cathode substrate and the anode substrate are applied with high pressure from the atmosphere.
Therefore, there is apprehension that the high pressure will cause the cathode and anode substrates disposed opposite to each other to be warped and broken. To prevent the foregoing problem, the FED has been structured such that the thickness of each of the cathode substrate and the anode substrate is enlarged to obtain predetermined strength against high pressures. When a FED having a width across corners of 5 inches is manufactured, a glass substrate having a thickness of about 5 mm is required. When a FED having a width across corners of 10 inches is manufactured, a glass substrate having a thickness of about 10 mm is required. Therefore, a FED having a light weight and small thickness cannot be manufactured.
It might therefore be feasible to employ thin glass substrates each having a thickness of, for example, 1.1 mm to manufacture a cathode substrate and an anode substrate. Moreover, spacers are disposed between the cathode substrate and the anode substrate. Thus, strength against the high pressure caused from the atmosphere is realized. The spacers are exemplified by bead spacers randomly disposed between the cathode substrate and the anode substrate; cylindrical spacers disposed in ineffective pixel regions between the cathode substrate and the anode substrate, and columnar or wall shaped spacers formed between the cathode substrate and the anode substrate by printing or photolithography.
When the bead spacers are employed, the portions in which the bead spacers are formed are made to be ineffective regions. Thus, the brightness of a formed image is lowered. When the distance between the cathode substrate and the anode substrate is elongated to improve electricity resistance between the cathode substrate and the anode substrate, the bead spacers must be enlarged. Hence it follows that the ineffective regions are undesirably enlarged. That is, when the bead spacers are employed, there arises a problem in that the elongation of the distance between the anode substrate and the cathode substrate causes the ineffective regions to undesirably be enlarged.
When columnar spacers are disposed, a plurality of spacers each having a high aspect ratio (height/diameter) are disposed. Therefore, satisfactory strength against high pressure cannot easily be obtained.
When the columnar or wall-shape spacers are employed, the foregoing spacers cannot easily be formed between the cathode substrate and the anode substrate, that is, in a space having a small height of about 1 mm to about 2 mm by printing or photolithography.
As described above, the conventional FED encounters a difficulty in reliably forming a spacer which does not lower the brightness of a displayed image and which has sufficient strength against high pressure. To overcome the foregoing problem, a structure in which a plate-like spacer is disposed has been disclosed in U.S. Pat. No. 564,847. The plate-like spacer is received between rail-like spacer guides provided for the cathode substrate and the anode substrate.
Therefore, spacer guides each having a high aspect ratio must precisely be provided for the cathode substrate and the anode substrate to dispose the plate-like spacer. However, the precise spacer guides each having the high aspect ratio cannot easily be provided for the cathode substrate and the anode substrate. Therefore, the method disclosed in U.S. Pat. No. 564,847 has a problem in that the spacer cannot easily and reliably be formed.
Accordingly, an object of the present invention is to provide an image display apparatus which is capable of overcoming the foregoing problems experienced with the conventional electron emission units, which does not lower the brightness of the displayed image, which has sufficient strength against high pressure and which permits a spacer to reliably be formed and a manufacturing method therefor.
To achieve the foregoing object, according to one aspect of the present invention, there is provided an image display apparatus comprising: an anode substrate having a structure in which at least an image display portion is formed on a first substrate; a cathode substrate in which at least electron emission units are formed on a second substrate and which is disposed opposite to the anode substrate; and spacers each of which is formed into a substantially rectangular shape and which are stood erect between the anode substrate and the cathode substrate, wherein two long sides of the spacer are secured to at least either of the anode substrate or the cathode substrate, and tensions are added to the spacers in the lengthwise direction of the spacers.
The image display apparatus according to the present invention and structured as described above incorporates the spacer stood erect between the anode substrate and the cathode substrate and capable of maintaining a predetermined distance between the anode substrate and the cathode substrate. The spacer of the image display apparatus is formed into a substantially rectangular shape. Tensions are added in a lengthwise pulling direction of the spacers, that is, in the lengthwise direction in which the spacer is elongated. Therefore, the spacer of the image display apparatus is able to prevent distortion and fracture even if the spacer is subjected to heat treatment.
To achieve the foregoing object, according to another aspect of the present invention, there is provided a method of manufacturing an image display apparatus having a structure that an anode substrate having a structure in which at least an image display portion is formed on a first substrate and a cathode substrate in which at least electron emission units are formed on a second substrate are disposed opposite to each other through spacers each of which formed into a substantially rectangular shape, the method of manufacturing an image display apparatus comprising the steps of: securing the two long sides of the spacers to at least either of the anode substrate or the cathode substrate, wherein tensions are added to the spacers in the lengthwise direction of the spacers.
The method of manufacturing an image display apparatus according to the present invention is structured such that the spacers are disposed between the anode substrate and the cathode substrate so that the cathode substrate and the anode substrate are disposed opposite to each other. The foregoing method is structured such that the spacers are secured in a state in which predetermined tensions are added in the lengthwise pulling direction of the spacer, that is, in a direction in which the spacer is elongated in the lengthwise direction. Therefore, the method according to the present invention is able to dispose the spacers without occurrence of distortion and fracture.